Improved detection of tides at Europa with radiometric and optical tracking during flybys

Park, Ryan; Bills, B. G.; Buffington, Brent; Folkner, W. M.; Konopliv, Alexander S.; Martin-Mur, Tomas J.; Mastrodemos, Nickolaos; McElrath, Timothy P.; Riedel, Joseph E.; Watkins, M. M.

doi:10.1016/j.pss.2015.04.005

Cited by 23 publications

(15 citation statements)

References 15 publications

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“…Europa is believed to have very high salinity (> 50 psu, unfeasible parameter regime is shaded in red in Fig.5b Applying our simplified model to Europa in Fig.5b, the predicted water-ice heat exchange becomes unphysically large (marked by the thick contour) when the equator-to-pole thickness variation is beyond 20% (marked by two horizontal blue dashed lines). This is consistent with the observation that the mean ice thickness is less 15 km (best match at 4 km) 31,44 and that no fissures such as the "tiger stripes" of Enceladus have been found. For icy moons with thicker ice shells, such as Dione, Titan, Ganymede, Callisto, the high pressure under the ice shell would remove the anoma-lous expansion for all salinities, making it impossible for the alpha and beta effects to cancel one another; meanwhile, the ice flow becomes very efficient, as it is proportional to the ice thickness cubed.…”

supporting

confidence: 91%

How does salinity shape ocean circulation and ice geometry on Enceladus and other icy satellites?

Kang

Mittal

Bire

et al. 2021

Preprint

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Of profound astrobiological interest is that not only does Enceladus have a water ocean, but it also appears to be salty, important for its likely habitability. Here, we investigate how salinity affects ocean dynamics and equilibrium ice shell geometry and use knowledge of ice shell geometry and tidal heating rates to help constrain ocean salinity. We show that the vertical overturning circulation of the ocean, driven from above by melting and freezing and the temperature dependence of the freezing point of water on pressure, has opposing signs at very low and very high salinities. In both cases, heat and freshwater converges toward the equator, where the ice is thick, acting to homogenise thickness variations. In order to maintain observed ice thickness variations, ocean heat transport should not overwhelm tidal heating rates within the ice, which are small in equatorial regions. This can only happen when the ocean’s salinity has intermediate values, order 20 psu. In this case polar-sinking driven by meridional temperature variations is largely canceled by equatorial-sinking circulation driven by salinity variations and a consistent ocean circulation, ice shell geometry and tidal heating rate can be achieved.

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supporting

confidence: 91%

How does salinity shape ocean circulation and ice geometry on Enceladus and other icy satellites?

Kang

Mittal

Bire

et al. 2021

Preprint

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“…An Io mission in Discovery would be more limited than New Frontiers concepts, for example using a fixed high-gain antenna (HGA) rather than a gimbaled HGA. However, the astrometry and gravity science can still be accomplished with a fixed HGA sometimes tracking Earth near Io plus strategically placed fan beam antennae, as planned for Europa Clipper (Park et al, 2015;Verma and Margot, 2018).…”

Section: Summary Recommendation: Spacecraft Mission To Iomentioning

confidence: 99%

Does Io Have a Magma Ocean?

McEwen¹,

Kleer²,

Park³

2019

Eos

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“…We placed a priori constraints on the uncertainties of coefficients of degree l > 2 in the expansion of the gravity field. The constraints follow a Kaula rule and we adopted the formulation given by Park et al (2015):…”

Section: Solve-for Parametersmentioning

confidence: 99%

Expected precision of Europa Clipper gravity measurements

Verma

Margot

2018

Icarus

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The primary gravity science objective of NASA's Clipper mission to Europa is to confirm the presence or absence of a global subsurface ocean beneath Europa's Icy crust. Gravity field measurements obtained with a radio science investigation can reveal much about Europa's interior structure. Here, we conduct extensive simulations of the radio science measurements with the anticipated spacecraft trajectory and attitude (17F12v2) and assets on the spacecraft and the ground, including antenna orientations and beam patterns, transmitter characteristics, and receiver noise figures. In addition to two-way Doppler measurements, we also include radar altimeter crossover range measurements. We concentrate on ±2 hour intervals centered on the closest approach of each of the 46 flybys. Our covariance analyses reveal the precision with which the tidal Love number k 2 , second-degree gravity coefficientsC 20 andC 22 , and higher-order gravity coefficients can be determined. The results depend on the Deep Space Network (DSN) assets that are deployed to track the spacecraft. We find that some DSN allocations are sufficient to conclusively confirm the presence or absence of a global ocean. Given adequate crossover range performance, it is also possible to evaluate whether the ice shell is hydrostatic.

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Improved detection of tides at Europa with radiometric and optical tracking during flybys

Cited by 23 publications

References 15 publications

How does salinity shape ocean circulation and ice geometry on Enceladus and other icy satellites?

How does salinity shape ocean circulation and ice geometry on Enceladus and other icy satellites?

Does Io Have a Magma Ocean?

Expected precision of Europa Clipper gravity measurements

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